Catalytic conversion of methane into benzene over ceria-zirconia-promoted molybdenum-supported zeolite for methane dehydroaromatization

The promotional effect of mixed ceria-zirconia oxides (CZO) over the Mo/HZSM-5 catalyst for methane dehydroaromatization (MDA) reaction was studied. The surface and structural properties of the synthesized catalyst were thoroughly exemplified using various microscopic and spectroscopic tools, and the correlation between catalytic properties and its performance for MDA reaction is discussed. The impregnation of CZO solid solution on Mo/HZSM-5 was monitored to give an excellent catalytic performance and improved benzene production rate (4.5 mu mol/gcat.s) related to the conventionally prepared Mo/HZSM-5 (3.1 mu mol/gcat.s) catalyst. In addition, a significant reduction in coke formation was examined in the CZO-modified Mo/HZSM-5 catalyst. The prevailing comprehension for higher catalytic activity could be because of the redox properties of CZO-deposited Mo/HZSM-5, which acts as a selective oxygen supplier and performs hydrogen combustion during the reaction, which is indirectly probed by residual gas analysis-mass spectroscopy, oxygen-temperature programmed desorption, and hydrogen-temperature programmed reduction analysis. The selective hydrogen combustion prevents the over-oxidation of aromatic species formed during the reaction, whereas the generated steam helps in reducing the coke content deposition in the MDA reaction. Thus, the advantage of CZO-incorporated Mo/HZSM-5 is manifested as it promotes the reaction equilibrium to shift towards the formation of benzene which is favourable for MDA reaction.